A physicist’s dream come true: Europe’s largest industrial solar thermal power plant | Technology

The industry is a devourer of resources, some as scarce as water and fossil fuels, and a polluter. However, transforming a factory into an energy-independent center, with no CO₂ emissions and which returns the equivalent of the supply used to waterways, is possible and profitable. This was the proposal of the doctor in physics and professor of thermodynamics at the University of Seville Valeriano Ruiz five years ago. Today, the dream of this reference in the clean energy sector, which did not survive (he died in 2021), is a reality and a technological model: the largest industrial solar thermal power plant in Europe, installed by the Engie company in the beer of the multinational Heineken in Seville.

The solar thermal installations, which occupy eight hectares of the factory land, have just started operating and have reduced by more than half the consumption of fossil gas for the thermal energy necessary for the production process (cooking and pasteurization), which which represents 65% of its demand. They hope to exceed 85% after this year. The remaining 35% of the energy needed is electric, mainly for bottling and cleaning, and they already produce it on their own: a solar plant in Huelva and another biomass plant in Jaén.

The brewing company’s overall investment in sustainability amounts to €30 million over the past two years. The equivalent of two thirds of this amount (20,476,668 euros, of which 13,369,356 come from European Feder funds) corresponds to the cost of the factory built by Engie in Seville, “Compensa”. The numbers are coming out,” says Tomás Madueño, engineer from the multinational that commissioned the project.

The strategy differs from that of other companies which limit themselves to purchasing additional energy from renewable sources to offset their emissions balances without reducing the use of polluting sources. “A compensation strategy based on the short-term operational impacts of emissions says nothing about the long-term effect,” warns Jesse Jenkinsprofessor at the Andlinger Center for Energy and the Environment and co-author of a Princeton University study published in Joule.

Wilson Ricks, a researcher at this American university, adds: “There are solar projects that do not compete with energy based on fossil fuels, but other solar projects that could have been built in their place. » According to him, “the most cost-effective approach for a company to declare net zero emissions relies almost entirely on acquiring enough solar or wind power to meet its annual consumption.”

Sagrario Sáez, director of sustainable development of Heineken, coincides. “If the plan is to offset, but you continue to produce with non-renewable energy, production and emissions increase.”

With this principle of zero emissions from renewable sources sufficient for the entire production process, the Seville factory was born. The eight hectares of parabolic mirrors concentrate sunlight in a central tube (collector) which, unlike installations for producing electricity using this system, contains only water instead of synthetic oil.

This liquid, as explained by Francisco Corral, engineer of Engie, reaches 210 degrees and is under pressure. From there it passes to a secondary circuit which, through exchangers, reduces the temperature to 160 degrees, which the factory needs to cook the cereals and pausterize the product. The power of this direct process is 30 thermal megawatts (MWt) per hour.

But this system would only allow its use under optimal conditions. To take advantage of all the solar thermal energy generated during solar radiation hours and keep the facility at full capacity at night or on days without sunlight, a warehouse was created to store 1,115 cubic meters of hot water. There are eight giant tanks insulated with 200 millimeters of carbon steel capable of delivering 68 MWt.

In the tanks, the water is distributed in layers of different temperatures, constantly monitored to release only the lowest when, cooled by mechanical means, it reaches the required degrees. A complex system of tortuous pipes, designed to resist expansion produced by heat, directly connects the water from the collectors and the water stored at the plant.

The principle is similar to that of well-known domestic solar water heaters, so it seems easy to think that its industrial application was obvious. However, the entire installation, unique in Europe, had to be generated from scratch. “The technology existed, but not on this scale,” Corral explains, pointing to facilities the size of eight football fields.

This was also not done before because the accounts needed to balance, for the investment, regardless of environmental and social compensation, to be profitable, which the rise in energy costs has accelerated. The factory was built in two years, almost twice as early as planned, in a process hampered by delays in accessing ERDF funds and which required 150,000 hours of work.

Engie is now the builder, owner and operator of the plant. In 20 years, it will transfer it to its customer Heineken, five years before the end of the theoretical useful life of the current installation. “There could be more,” says Corral. “This is the lifespan of power plants, which withstand temperatures of up to 350 degrees.”

This useful life is essential to the profitability of these installations. In this sense, Stefaan De Wolf, researcher at the KAUST Solar Center and main author of a work published in Science, warns: “Deployed solar panels must have a useful life of several decades. Understanding degradation rates is crucial to establishing competitive pricing and warranties.

And, in addition to the economic reason, there is the environmental problem due to the production of waste when the installations become obsolete. Sagrario Sáez assures that the zero waste and full recycling policy agreed for the entire production process will also apply to the new facility. The panels used are essentially mirrors and do not use the toxic and rare materials of other systems, such as perovskite.

This project will be reproduced, with different technology and scale, in the Heineken factory in Valencia, which will open its doors on February 28, according to forecasts. But the creators of the whole system believe that it is applicable to any industrial process that requires heat for manufacturing and has land next to the factory, because distance is the main degrader of the power obtained .

Water

Even though the chosen system (concentrated solar power or CSP) consumes much less water than tower plants, Valeriano Ruiz’s dream was still unfulfilled. A brewery, by pure logic, is a consumer of water. In traditional systems, more than three liters of this resource are required for each of the final products.

The Seville factory, where water is oil, has managed to reduce this proportion to 2.6 liters for every liter of beer. Of this total, the majority is part of the product consumed (95% of a beer is water), half a liter evaporates during the process and part of the remainder is reused for uses other than beer. consumption. “Every drop counts,” emphasizes Sagrario Sáez. But the objective was more ambitious: to recover 1.9 billion liters.

The strategy in this case was to focus on natural water reservoirs that have been deteriorated and rendered unusable by human action. A canal naturally creates the equivalent of artificial storm reservoirs, spaces where water from precipitation is stored.

On the Jarama River in Madrid, a former cement factory destroyed a natural wetland by creating a dam to prevent flooding at the factory. The factory abandoned the enclave and left the plug. The recovery of the natural space has brought new life to the lagoon and animal tracks once again mark its banks. The same strategy was used in several enclaves around Doñana. In the Valencian Albufera, the objective was to eliminate kilometers of reeds, an invasive grass introduced in the 16th century that alters the environment and dries it out.

The intervention in half a dozen natural areas made it possible to return to the basins the millions of liters of water planned with an investment of one million euros.

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